1. Field of the Invention:
This invention relates to improvements in a sequential control signal generator which has a plurality of key switches and is adapted to produce a sequential control signal having a sequential arrangement of a plurality of control signals by a sequential operation of the key switches.
2. Description of the Prior Art:
A sequential control signal having a sequential arrangement of a plurality of control signals is employed for a remote control of a variety of devices to be controlled, such, for example, as an automatic answering telephone set.
The automatic answering telephone set has a function of reproducing an answering message recorded on a magnetic tape and sending the reproduced message to a calling party from an outside telephone set in response to a call from the calling party. Accordingly, the automatic answering telephone set requires control signals for reproducing and sending an answering message from the outside telephone set. The control signals needed for such an automatic answering telephone are, for instance, a control signal for fast forwarding the magnetic tape having recorded thereon the answering message, a control signal for rewinding the magnetic tape, a control signal for sustaining the answering message reproducing state, etc. Such a plurality of control signals are sequentially obtained by actuating a plurality of key switches one after another. The plurality of control signals thus obtained will hereinafter be referred to as the sequential control signals. An error in the order of arrangement of the sequential control signals will leads to an erroneous operation of the automatic answering telephone set. Now, let it be assumed that the automatic answering telephone set needs three control signals. For the sake of clarity, let it be assumed that these three control signals are first, second and third control signals and are obtained by the actuation of first, second and third key switches, respectively. Further, assume that unless the first control signal is followed by the second or third control signal, the automatic answering telephone set performs a faulty operation. In such a case, if the actuation of the second or third key switch precedes that of the first key switch, the result is a malfunction of the automatic answering telephone set. The second or third key switch operation before the first key switch operation will hereinafter be referred to as the erroneous key switch actuation.
In conventional sequential control signal generator for generating such a sequential control signal necessary for the automatic answering telephone set, no consideration is paid to the likelihood of the erroneous key switch actuation. Consequently, the conventional sequential control signal generators has the defect of producing a sequential control signal having a sequential arrangement of a plurality of control signals following the order of the erroneous key switch actuation.